Give an example of a force that merely changes the direction of motion of a body.

$A$ block is supported by a cord $A$ from a rigid support,and another cord $B$ is attached to the bottom of the block. If you give a sudden jerk to $B$,it will break. But if you pull on $B$ steadily,$A$ will break. Why?

$(a)$ Define inertia. You are provided with three bodies made of wood,rubber,and iron of the same shape and size. Which one of them will have greater inertia? Explain it.
$(b)$ When a striker hits the bottom of the pile of coins placed at the centre of a carom board,only the lowest coin is removed. Give reason for it.

An object experiences a net zero external unbalanced force. Is it possible for the object to be moving with a non-zero velocity? If yes,state the conditions that must be placed on the magnitude and direction of the velocity. If no,provide a reason.

$A$ bullet of mass $5 \, g$ travelling at a speed of $120 \, m s^{-1}$ penetrates deeply into a fixed target and is brought to rest in $0.01 \, s$. Calculate: $(a)$ the distance of penetration in the target,$(b)$ the average force exerted on the bullet.

$(a)$ When a motorcar makes a sharp turn at a high speed,we tend to get thrown to one side. Why?
$(b)$ State Newton's first and third law of motion.
$(c)$ $A$ force of $5 \ N$ gives a body of mass $m$ an acceleration of $10 \ m \ s^{-2}$. Calculate the mass of the body in grams.